So, I may be entirely wrong here, but I thought it’s only considered a handball if intent can be reasonably presumed (or you’re doing something wildly stupid with your arms, the ball hits them and drastically changes direction etc)?

As I say, I could be totally wrong with that, but I don’t see how this would count as a handball if I’m not. Definite contact with the forearm, but zero chance of intent or even ability to expect it, really.